It is known that a slow motion video "special effect" may be obtained by recording the video signal on a suitable medium (e.g. disc or tape) and repeating fields of the recorded signal during playback. For example, half-speed slow motion may be obtained in a video tape recorder by scanning each recorded field twice before advancing the tape to the next field. Video tape recorders having such a variable speed playback feature are commercially available for the professional (i.e., studio) and consumer markets.
It has been recognized that the images obtained by conventional repeat field playback lack the qualities of smoothness of motion characteristic of slow motion film. The reason is that in film slow motion production, the camera is speeded up to take more pictures per second at a higher film and shutter speed thereby increasing the temporal resolution of recorded images and reducing the tendency for fast moving objects to jerk or to appear blurred. It would be desirable to apply the principles of slow motion film production to video production to provide a smoother and sharper slow motion image. To do this, one might consider increasing the camera scanning speed in a manner analogous to slow motion film cameras. While such an approach has the virtue of simplicity, it also has the disadvantage of rendering the bandwidth of the video signal a direct proportional function of the slow motion speed of the camera. The problem is that as camera speed is increased, the video signal bandwidth also increases until a point is reached where the video bandwidth exceeds the capability of the recorder used to ultimately provide playback of the signal. A further difficulty is that video tape (or disc) recorders are typically optimized to record signals of a given bandwidth and so where a number of slow motion speeds are desired it may be necessary to make substantial and complex modifications or adaptations of the recorder to accomodate varying bandwidths of the video signal.